The overall objective of the current research is to investigate the possible involvement of nucleosome core histone hyperacetylation as a facilitiating mechanism for the transformation of chromatin into a biochemical and/or structural state capable of being actively transcribed by polymerases into RNA transcripts. The more specific aims of the project are to determine the biochemical mechanisms that regulate the levels of nucleosome histone acetylation in various restricted regions of nuclear chromatin. To achieve this goal, we are in the process of biochemically purifying the various histone deacetylase and acetyltransferase enzymes from mouse Friend erythroleukemic cells growing in tissue culture for detailed biochemical studies and for specific antibody production against each of the types of enzymes. Furthermore, we have recently discovered that non-histone proteins of the "High Mobility Group" (HMGs), specificilly either HMG-14 or HMG-17, which are associated with "active" chromatin in these mouse cells are also partial inhibitors of the histone deacetylase enzymes. It thus appears that these small proteins may well be involved in the control of the levels of histone acetylation in "active" chromatin in mouse cells. We are therefore investigating the ways these proteins interact with the deacetylase enzymes and their localization within various nucleosome and sub-nucleosome chromatin fractions. Another area of investigation concerns the effect of sodium butyrate (an inhibitor of histone deacetylases) on the gene expression in various tissue culture cell types and in Drosophila melanogaster. We have demonstrated that this short-chain fatty acid is capable of inducing new gene expression in mouse tissue culture cells and also capable of supressing position-effect variegation (and thus of inducing new gene activity) in Drosophila. These experiments are currently being extended along a number of lines, including a search for cells or organisms with mutations in the histone deacetylase enzymes.